Red, green and blue Light Emitting Diodes (LEDs), which may realize very bright white light, have been developed based on the development of, for example, a gallium nitride (GaN) metal organic chemical vapor deposition method and a molecular beam growth method.
These LEDs substitute for conventional light sources because they include no environmentally noxious materials, such as mercury (Hg), which are used in conventional lighting appliances, such as, for example, incandescent lamps and fluorescent lamps, thus being very environmentally friendly, and also have several advantages, such as, for example, a long lifespan and low power consumption. The salient competitiveness of the LEDs is to realize high brightness through high-efficiency and high-output chip and packaging technologies.
FIG. 1 is a schematic sectional view of a conventional light-emitting device package, which includes a package body 10 having a cavity C, an LED 20, a glass 30, and an adhesive 40.
Considering the process of manufacturing the conventional light-emitting device package illustrated in FIG. 1, after the adhesive 40 is deposited on the upper surface of the package body 10 close to the cavity C, the glass 30 is pushed by a force of about 400 gf so as to be bonded to the package body 10. At this time, as the adhesive 40 is introduced into the cavity C by the force pushing the glass 30, as illustrated in FIG. 1, the function of reflecting light at the slope of the cavity C may be prevented by the adhesive 40 that has been introduced into the cavity C.
In addition, in the case where the LED 20 emits light in a wavelength band of deep ultraviolet light, when the adhesive 40 introduced into the cavity C is exposed to deep ultraviolet light for a long time to thereby be discolored, a great quantity of light is absorbed by the introduced adhesive 40, which may cause deterioration in light emission efficiency. In particular, in the case where the adhesive 40 is formed of silicon or epoxy, the adhesive 40 is discolored and thereafter decomposed, which may break the bond between the glass 30 and the package body 10, and may reduce the lifespan of the light-emitting device package due to, for example, the entry of moisture through, for example, micro cracks formed in the light-emitting device package.
In addition, the adhesive 40 may also serve to prevent external moisture or water from being introduced into the cavity C. However, when an external foreign substance 50 is in a gaseous state, for example, when gas molecules including water molecules permeate from the outside, the adhesive 40 may have difficulty in completely blocking them. In particular, when the light-emitting device package is operated for a long time in a high-temperature and high-humidity environment, for example, moisture or water may enter the cavity C, thereby causing discoloration of, for example, a plated portion of the light-emitting device package and an electrode portion of the LED 20, which may further deteriorate the lifespan and performance of the light-emitting device package.